Such a kind of matrix converter as conventionally present is a conversion device in which bidirectional switches using self-commutating semiconductor elements are changed at a high speed to convert a single phase or a multi-phase AC input into an electric power having an arbitrary voltage or frequency and configured as shown in FIG. 1
FIG. 1 shows a basic configuration of a three-phase/three-phase matrix converter. A three-phase AC power source 1 is connected to an arbitrary load 4 via an input filter section 2 constituted by reactors and capacitors and a semiconductor power conversion section 3 constituted by nine bidirectional switches (SW1 through SW9). Nine bidirectional switches SW1 through SW9 are constituted by 18 reverse blocking IGBTs, combinations of semiconductor elements such as ordinary IGBTs and diodes, or so forth. Although no bones of detailed configuration methods thereof are made, switching elements which are capable of being power supplied or power received in both directions constitute the above-described nine bidirectional switches.
It should be noted that, as shown in FIG. 1, power source three phases are RST phases and output three phases are UVW phases.
Non-patent documents 1 through 4 have conventionally described various space vector modulation methods for the matrix converters.
The AC-AC direct conversion device represented by the matrix converter is a combination form of a voltage source power converter in which a power source voltage is PWM controlled to generate an output voltage thereof and a current source power converter in which an output load current is deemed to be a current source and a PWM control causes a power source current thereof to be generated and is a direct power conversion device from the alternating current to the alternating current. In order to realize a simultaneous control for both of the power converters by the nine bidirectional switches, mutual controls are associated with each other (that is to say, a restriction condition such that instantaneous three-phase effective powers supplied and received between the input thereof and the output thereof needs to be coincident with each other is provided).
Next, the space vector of the matrix converter will, herein, be defined with the above-described matters taken into consideration. The output voltage of the matrix converter is generated from an AC power source voltage and the input current thereof is generated in the PWM method from an AC load current. Hence, as is different from the space vector of a generally available DC-AC conversion device (an inverter), an instantaneous space vector through the PWM control that can be generated by the matrix converter is fluctuated moment by moment. A fluctuation in the instantaneous space vector of the space vector of the output voltage side is dependent upon the phase and magnitude of the power source voltage which provides a base for chopping in the PWM method. The instantaneous space vector of the input current side is fluctuated in dependence upon the phase and magnitude of the output load current.
In addition, a switching pattern of the matrix converter is needed to give such restriction conditions that (1) a power source short-circuit does not occur and (2) a discontinuity of the load current does not occur. The above item (1) provides a purpose to prevent an excessive current breakage due to the power source shortage and the above item (2) provides a purpose to prevent an excessive voltage failure due to an energy stored in an inductance in an inductive load. With these conditions taken into consideration, the switching patterns of nine bidirectional switches SW1 through SW9 are limited to 27 kinds (33) of combinations.
If the 27-kind switching patterns are expanded on a stationary αβ coordinate at the input side and the output side, these switching patterns can be expressed as Table 1.
TABLE 1MCMCI/OswitchconnectON stateGroupStateUVWUVWS1simple1s1-1aRSS158harmonic2s1-1bSRR247oscillation3s1-2aSTT2694s1-2bTSS3585s1-3aTRR3476s1-3bRTT169S2simple7s2-1aSRS248harmonic8s2-1bRSR157oscillation9s2-2aTST35910s2-2bSTS26811s2-3aRTR16712s2-3bTRT349S3simple13s3-1aSSR257harmonic14s3-1bRRS148oscillation15s3-2aTTS36816s3-2bSST25917s3-3aRRT14918s3-3bTTR367R1counter-19r1-1RST159clockwise20r1-2TRS348rotation21r1-3STR267R2clockwise22r2-1RTS168rotation23r2-2SRT24924r2-3TSR357Znull25z1RRR14726z2SSS25827z3TTT369
In Table 1, the space vector is divided into six groups of: simple harmonic oscillation vectors S1 of simple harmonic oscillation vector groups, each vector with a direction of a phase angle of 30 degrees as a positive axis; simple harmonic oscillation vectors S2, each vector with the direction of the phase angle of 150 degrees as the positive axis; simple harmonic oscillation vectors S3, each vector with the direction of the phase angle of 270 degrees as the positive axis; rotation vectors R1, each vector having a maximum constant length and rotating in a counterclockwise direction; rotation vectors R2, each vector having the same constant length and rotating in a clockwise direction; and zero vectors Z, each vector being fixed on a center zero point of a hexagon. These respective base vectors are dependent upon phase θ of the input voltage. In other words, these respective base vectors are fluctuated in synchronization with an angular speed ωi of the input voltage. In addition, a length of each base vector (a magnitude of a hexagon) corresponds to the magnitude of an input line voltage.
As described before, since the instantaneous space vectors are changed moment by moment, they are fluctuated in synchronization with the respective phases. When attention is paid to the direction of fluctuation of the instantaneous space vectors on the stationary αβ coordinate, 27 kinds of vectors can be classified into 18 kinds of simple harmonic oscillation vectors (respective six kinds on three axes and respective phase relationships are constant), six kinds of rotation vectors (three kinds in the clockwise direction, three kinds in the counterclockwise direction, and the respective magnitudes are constant), and remaining three kinds of zero vectors (invariable at a position of an origin).
Table 1 is an example of the classification of 27-kind patterns with an output side space vector as a reference. Such a basic concept of the space vector as described above is well known from non-patent document 4 or so forth.
Non-patent documents 1 and 2 describe a method directly considering states of the input three-phase voltage and connections of nine switches from desired three-phase output voltage and three-phase input current (an AC-AC direct conversion method). It is a purpose to reduce output voltage harmonics and to prevent a switch change between an input maximum voltage phase and an input minimum voltage phase. In addition, it is effective for reducing a power loss and a noise reduction.
Non-patent documents 1 and 2 have proposed an addition of the following conditions to a switching pattern generation condition within a control period T in a conventional AC/AC direct conversion method.
1. Commutations from the input maximum voltage phase to the minimum voltage phase and from the minimum voltage phase to the maximum voltage phase are inhibited.
2. An input minimum voltage phase is not connected to a maximum voltage phase of an output voltage command. An input maximum voltage phase is not connected to a minimum voltage phase of the output voltage command.
FIG. 2 shows examples of the switching patterns and the output voltage to which the above-described conditions are added. FIG. 2(a) shows a case where an output voltage command value is high and FIG. 2(b) shows a case where the output voltage command value is low, respectively (it should be noted that Figs. (a) and (b) of 2 indicate a case when input phase voltage R phase>S phase>T phase and output command value phase voltages U phase>V phase>W phase.
As a technique to generate the above-described switching patterns, a triangular wave comparison method can be utilized which is a simple technique which has conventionally and frequently been used. Duties to turn on three switches respectively connected to respective phases of the output of the matrix converter are calculated and, thereafter, carrier comparisons are made separately for the respective output phases to determine pulse output duration times.
A method described in non-patent document 3 adopts a method in which, after duty values are calculated through a conventional virtual indirect modulation method, the calculated duty values are expanded to the carrier comparisons separately for respective three phases as described in non-patent document 1, in view of the fact that the conventional duty calculations are based on a direct AC/AC conversion form and the duty calculations that the direct AC/AC conversion form naturally has need to provide such a condition that the three-phase effective power is constant.
This method has a maximum feature that, although a stage at which the duties are calculated is in the virtual indirect modulation method, the same pulse pattern as the AC/AC direct conversion modulation method is obtained after the three-phase separate comparison.
Non-patent document 3 describes that the space vector at an input virtual rectifier and the space vector at an output virtual inverter are obtained from a power source voltage detection value and the output voltage command as shown in FIG. 3. At the same time, as shown in FIG. 4, sector information of the input and output command vectors and a magnitude relationship information of input power source R, S, and T phases and output U-phase, V-phase, and W-phase are obtained.
It should, herein, be noted that the sector information will be explained. The input current command and the output voltage command are three-phase to two-phase converted to obtain their respective instantaneous space command vectors. In addition, switching combinations of the virtual rectifier and the virtual inverter define the respective space vectors as shown in FIG. 3. At this time, command vectors such as to draw circle loci in spaces in FIG. 3, namely, provide three-phase sinusoidal wave current and voltage commands, respectively. Herein, these space are partitioned as shown in FIG. 4. In a case of the input current space vector of FIG. 4(a), when the phase of the input current command vector is from zero degrees (0) to 30 degrees, sector 1 is defined and when the phase of the input current command vector is from 30 degrees to 60 degrees, sector 2 is defined. In the same way, when the space partition is continued over 360 degrees, twelve sectors of sector 1 through 12 can be defined according to the phase. In a case of the output voltage command vector, six sectors for each of 60 degrees can be defined.
Base vectors IA, IB at the input rectifier side utilized to constitute the input current command vector and duties dA, dB per unit time (a control period) for the base vectors are obtained through calculations from the information on the input current command vector (refer to a second item of non-patent document 3).
In the same way, base vectors VX, VY at the output side to be utilized and duties dX, dY for the base vectors described above are obtained through the calculations, as shown in FIG. 5 from the information on the output voltage command vector. It should be noted that Iin* in FIG. 5(a) denotes the input current command vector and Vout* in FIG. 5(b) denotes the output voltage command vector, respectively.
Then, the input side duties are synthesized with the output side duties so that the switching pattern of the matrix converter and the duties thereof shown in FIG. 6 can be obtained. The sector information on the input and output command vectors and the switching pattern of the matrix converter to be outputted through the synthesis of the input and output duties are as shown in Table 2.
TABLE 2Rectifier1(R > S > T)RSRT2(R > S > T)RTST3(S > R > T)RTSTInverterAXAYBXBYZAXAYBXBYZAXAYBXBYZ1(U > V > W)100 110RSSRRSRTTRRTSSSRTTRRTSTTSSTSSSRTTRRTSTTSSTRRR2(V > U > W)110 010RRSSRSRRTTRTSSSRRTTRTSSTTSTSSSRRTTRTSSTTSTRRR3(V > W > U)010 011SRSSRRTRTTRRSSSTRTTRRTSTTSSSSSTRTTRRTSTTSSRRR4(W > V > U)011 001SRRSSRTRRTTRSSSTRRTTRTSSTTSSSSTRRTTRTSSTTSRRR5(W > U > V)001 101SSRRSRTTRRTRSSSTTRRTRTTSSTSSSSTTRRTRTTSSTSRRR6(U > W > V)101 100RSRRSSRTRRTTSSSRTRRTTSTSSTTSSSRTRRTTSTSSTTRRRRectifier4(S > R > T)STSR5(S > T > R)STSR6(S > T > R)SRTRInverterAXAYBXBYZAXAYBXBYZAXAYBXBYZ1(U > V > W)100 110STTSSTSRRSSRRRRSTTSSTSRRSSRTTTSRRSSRTRRTTRTTT2(V > U > W)110 010SSTTSTSSRRSRRRRSSTTSTSSRRSRTTTSSRRSRTTRRTRTTT3(V > W > U)010 011TSTTSSRSRRSSRRRTSTTSSRSRRSSTTTRSRRSSRTRRTTTTT4(W > V > U)011 001TSSTTSRSSRRSRRRTSSTTSRSSRRSTTTRSSRRSRTTRRTTTT5(W > U > V)001 101TTSSTSRRSSRSRRRTTSSTSRRSSRSTTTRRSSRSRRTTRTTTT6(U > W > V)101 100STSSTTSRSSRRRRRSTSSTTSRSSRRTTTSRSSRRTRTTRRTTTRectifier7(T > S > R)SRTR8(T > S > R)TRTS9(T > R > S)TRTSInverterAXAYBXBYZAXAYBXBYZAXAYBXBYZ1(U > V > W)100 110SRRSSRTRRTTRSSSTRRTTRTTSTSSSSSTRRTTRTSSTTSRRR2(V > U > W)110 010SSRRSRTTRRTRSSSTTRRTRTTSSTSSSSTTRRTRTTSSTSRRR3(V > W > U)010 011RSRRSSRTRRTTSSSRTRRTTSTSSTTSSSRTRRTTSTSSTTRRR4(W > V > U)011 001RSSRRSRTTRRTSSSRTTRRTSTTSSTSSSRTTRRTSTTSSTRRR5(W > U > V)001 101RRSSRSRRTTRTSSSRRTTRTSSTTSTSSSRRTTRTSSTTSTRRR6(U > W > V)101 100SRSSRRTRTTRRSSSTRTTRRTSTTSSSSSTRTTRRTSTTSSRRRRectifier10(T > R > S)TSRS11(R > T > S)TSRS12(R > T > S)RSRTInverterAXAYBXBYZAXAYBXBYZAXAYBXBYZ1(U > V > W)100 110TSSTTSRSSRRSRRRTSSTTSRSSRRSTTTRSSRRSRTTRRTTTT2(V > U > W)110 010TTSSTSRRSSRSRRRTTSSTSRRSSRSTTTRRSSRSRRTTRTTTT3(V > W > U)010 011STSSTTSRSSRRRRRSTSSTTSRSSRRTTTSRSSRRTRTTRRTTT4(W > V > U)011 001STTSSTSRRSSRRRRSTTSSTSRRSSRTTTSRRSSRTRRTTRTTT5(W > U > V)001 101SSTTSTSSRRSRRRRSSTTSTSSRRSRTTTSSRRSRTTRRTRTTT6(U > W > V)101 100TSTTSSRSRRSSRRRTSTTSSRSRRSSTTTRSRRSSRTRRTTTTT
Using five switching patterns and duties obtained as described above, the expansion to the duties of the input phases of R, S, and T connected to output phases U, V, and W, respectively, is again carried out. For each of the phases, the duties associated with an input voltage maximum phase, an input voltage middle phase, an input minimum phase are derived in a form of sum of virtual duties. The duties thus obtained are used to obtain the patterns through the carrier comparisons shown in FIG. 7 so as to provide the minimum phase→middle phase→maximum phase→middle phase→minimum phase of the input voltage. The synthesis of the patterns obtained for each of the output phases can obtain the switching patterns which are the same as those described in non-patent documents 1 and 2.    Non-patent document 1: “PWM Control of Three-Phase to Three-Phase Matrix Converter for Reducing Output Voltage Harmonics” by Hiroshi Shimada and Takeharu Takeshita in Semiconductor Power Conversion Study Circle SPC-05-48 (2005).    Non-patent document 2: “Matrix Converter Control Using Direct AC/AC Conversion Approach to Reduce Output Voltage Harmonics” by Hakaharu Takeshita and Hiroshi Shimada in Electrical Engineering Society paper magazine D, Vol. 126 No. 6 (2006).    Non-patent document 3: “Improvement of Pulse Pattern for Space Vector Modulated Matrix Converter” by Kiichiro Yamamoto, Katsuji Shinohara, and Tatsuya Mori in Semiconductor Power Conversion Study Circle SPC-06-159 (2006).    Non-patent document 4: “A Study of Space Vector Modulation Method for Three-Phase to Three-Phase Matrix Converter” by Yugo Tadano, Shota Urushibata, Masakatsu Nomura, and Tadashi Ashikaga in a mass meeting of electrical engineering society industrial application department in Heisei 18 1-04-4 (2006).